Most babies are born healthy, but there is still a small risk for all women to give birth to a baby with some type of anomaly. Ultrasound has proven to be one of the most reliable procedures to prenatally diagnose some of these conditions. Ultrasound can be used during the entire pregnancy, but in the first trimester ultrasound examinations are, as a rule, used to exactly calculate the pregnancy, to recognize multiple fetuses, to prove the vitality of the fetus, as well as for early diagnosis of serious fetal abnormalities. Between the 11th and the 14th week of pregnancy, ultrasound is also used to determine whether increased nuchal translucency is present. This is the most effective screening method for Trisomie 21 and all important chromosome anomalies.